Since optical discs such as a CD (Compact Disc) and a CD-ROM (Compact Disc Read Only Memory) are easy to handle and are produced at relatively low cost, they have been widely used as recording mediums for storing data. In recent years, a CD-R (Compact Disc Recordable) disc, on which data can be recorded once, and a CD-RW (Compact Disc ReWritable) disc, on which data can be rewritten, have come out. Thus, data can be more easily recorded on such recordable optical discs than before. As a result, optical discs such as a CD-DA disc, a CD-ROM disc, a CD-R disc, and a CD-RW disc have become the mainstream of data recording mediums. In addition, in recent years, audio data is compressed according to the MP3 (MPEG1 Audio Layer-3) and the ATRAC (Adaptive TRansform Acoustic Coding) 3 and recorded on the CD-ROM disc, the CD-R disc, the CD-RW disc, and so forth.
However, as a CD-R disc and a CD-RW disc have come out, data recoded on a CD-DA disc and a CD-ROM disc can be more easily copied than before. As a result, a problem about copyright protection has arisen. Thus, when content data is recorded to a recordable optical disc, it is necessary to take measures to protect content data.
As a method for protecting content data recorded on a CD-DA disc and a CD-ROM disc, it is determined whether the objective disc is an original disc or a disc whose content data has been copied from an original disc (hereinafter referred to as copied disc). When the objective disc is an original disc, a copy operation can be permitted. In contrast, when the objective disc is a copied disc, a further copy operation can be prohibited.
To determine whether the objective disc is an original disc or a copied disc, the following method has been proposed. In the proposed method, an error is intentionally inserted into predetermined data. When content data is reproduced from the objective disc, depending on whether or not the inserted error is detected, it is determined whether the objective disc is an original disc or a copied disc. However, in that method, since a part of data is an error, the method cannot be used as a conventional standard such as the CD standard. In addition, it is difficult to bury desired data such as an encryption key in predetermined data.
Therefore, an object of the present invention is to provide a data recording medium, a data recording method, a data recording apparatus, a data reproducing method, a data reproducing apparatus, a data transmitting method, and a data receiving method that allow desired information to be buried and used as a format standard.